To provide an interlayer displacement measuring apparatus capable of being easily installed at low costs and highly accurately measuring interlayer displacements.

The interlayer displacement measuring apparatus includes an invar steel wire 10 of which both ends 12 are fixed to the vicinity of an upper-layer floor 1 and the vicinity of a lower-layer floor 2 and which is extended in brace shape between layers by a spring 11; a strain gauge 20 for detecting the amount of extension and contraction of the spring 11; and deflection stoppers 15 for allowing displacements of the invar steel wire 10 in its longitudinal direction and restricting the invar steel wire 10 from deflecting in directions intersecting with its longitudinal direction. The deflection stoppers 15 are arranged at prescribed intervals from one another along the longitudinal direction of the invar steel wire 10.